I actually posted a question to quora, "Is it legal to use review information from websites to calculate an average score?"
Replied:
"In the US, so long as you have the legal right to access the data to begin with (i.e., you didn't crack into someone's system to get it), yes. Simple facts, and things like mathematical analysis of those facts, cannot be copyrighted.
Calculating an average is just a mathematical process. It doesn't require the type of creativity that would allow for copyright."
Though I am not a 100% sure if just the out of 5 or % number usage counts or not.